An Effective Specific Heat Model of the Heat Transfer in a Micro-PCM Suspension in Laminar Tube Flow

2002 ◽  
Author(s):  
James C. Mulligan ◽  
Richard D. Gould
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Specific Heat ◽  
Computational Analysis ◽  
Heat Rate ◽  
Tube Flow ◽  
System Flow ◽  
Effective Specific Heat ◽  
Latent Effects ◽  
Laminar Tube Flow

An “effective” specific heat model of the heat transfer in the thermal entry region of a laminar tube flow carrying a microPCM fluid is presented. The model is in an analytical format and intended to be easy to apply. It is based on classical Graetz theory, along with a computational analysis of entry region heat transfer that includes the latent effects contributed by a suspended microPCM. Generally, the Nusselt number of a microPCM fluid is shown to be of the following general form Nu = f(Gr, L, P), where Gr is the classical Graetz number, and L and P are Stefan-like parameters defined as: Fλ/Cp(Tl−Ts) and Cp(Ts−Tin)/(q/m)˙, respectively. Here F is the fraction of PCM in the suspension, λ the latent heat, and q/m˙ the ratio of the system heat rate to the system flow rate.

Heat transfer and reaction in laminar tube flow

AIChE Journal ◽  
1966 ◽  
Vol 12 (2) ◽  
pp. 213-220 ◽  
Author(s):  
R. I. Rothenberg ◽  
J. M. Smith
Keyword(s):  
Heat Transfer ◽  
Tube Flow ◽  
Laminar Tube Flow

scholarly journals Computational analysis of convective heat transfer across a vertical tube

2021 ◽  
Vol 49 (4) ◽  
pp. 932-940
Author(s):  
Jashanpreet Singh ◽  
Chanpreet Singh
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Computational Analysis ◽  
Numerical Data ◽  
Vertical Tube ◽  
Steady State Condition ◽  
Convective Mode ◽  
Good Agreement

This paper deals with the numerical investigation of the convective mode of heat transfer across a vertical tube. Experiments were carried out using air as a fluid in a closed room by achieving a steady-state condition. Implicit scheme of finite difference method was adopted to numerically simulate the free convection phenomenon across vertical tube using LINUX based UBUNTU package. Numerical data were collected in the form of velocity, temperature profiles, boundary layer thickness, Nusselt number (Nu), Rayleigh's number (Ra), and heat transfer coefficient. The results of the Nusselt number showed a good agreement with the previous studies. Results data of heat transfer coefficient indicate that there were some minor heat losses due to radiation of brass tube and curvature of the tube.

Unsteady Laminar Forced-Convective Tube Flow Under Dynamic Time-Dependent Heat Flux

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
M. Fakoor-Pakdaman ◽  
Mehdi Andisheh-Tadbir ◽  
Majid Bahrami
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Analytical Model ◽  
Time Dependent ◽  
Bulk Temperature ◽  
Fluid Temperature ◽  
Tube Flow ◽  
Flux Boundary Condition ◽  
Arbitrary Time

A new all-time model is developed to predict transient laminar forced convection heat transfer inside a circular tube under arbitrary time-dependent heat flux. Slug flow (SF) condition is assumed for the velocity profile inside the tube. The solution to the time-dependent energy equation for a step heat flux boundary condition is generalized for arbitrary time variations in surface heat flux using a Duhamel's integral technique. A cyclic time-dependent heat flux is considered and new compact closed-form relationships are proposed to predict (i) fluid temperature distribution inside the tube, (ii) fluid bulk temperature and (iii) the Nusselt number. A new definition, cyclic fully developed Nusselt number, is introduced and it is shown that in the thermally fully developed region the Nusselt number is not a function of axial location, but it varies with time and the angular frequency of the imposed heat flux. Optimum conditions are found which maximize the heat transfer rate of the unsteady laminar forced-convective tube flow. We also performed an independent numerical simulation using ansys fluent to validate the present analytical model. The comparison between the numerical and the present analytical model shows great agreement; a maximum relative difference less than 5.3%.

Accuracy of Thermocouples in Transient Surface Temperature Measurements Dominated by Radiant Heating

2014 ◽  
Author(s):  
K. S. Jhajj ◽  
E. F. J. R. Caron ◽  
N. L. Chester ◽  
K. J. Daun
Keyword(s):  
Heat Transfer ◽  
Specific Heat ◽  
Strong Influence ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Radiant Heating ◽  
Muffle Furnace ◽  
Coating Application ◽  
Specific Heats ◽  
Effective Specific Heat

In hot forming die quenching, furnaces are used to austenitize steel blanks and transform an Al-Si layer into a permanent Al-Si-Fe coating. Application of a simplified heat transfer model to thermocouple measurements on steel blanks heated in industrial furnaces showed specific heats that varied with blank thicknesses, raising questions about the accuracy of these measurements. A detailed experimental study on a lab scale muffle furnace shows that natural convection and variations in the surrounding temperatures has a strong influence on the inferred specific heat. An improved heat transfer model is used to qualitatively assess how austenitization influences the effective specific heat.

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